Human immunodeficiency virus (HIV) is known to cause acquired immune deficiency syndrome (AIDS), and because the HIV exhibits rapid genetic drift, widely divergent strains are emerging. Thus, detection and treatment of variant strains have proven to be challenging and difficult.
The diagnosis of HIV infection is most commonly achieved by detecting antibody against HIV. Methods for laboratory diagnosis of HIV infection have evolved and offered a large number and a variety of effective methods that can prolong and improve the quality of life for HIV infected patients. In the industrialized countries, enzyme immunoassay (EIA) is the most commonly used method. The assay is comprised of an immobilized viral antigen, which may be comprised of viral lysate, retrovirus proteins or natural or synthetic polypeptides, that reacts with blood or serum components suspected of containing HIV antibodies. Although there is a window stage problem (limiting to the anti-HIV antibody generation time) for the EIA detection, it is still the most popular for HIV diagnosis due to excellent sensitivity, good specificity, and relatively lower cost.
However, there are some disadvantages of the use of isolated viral proteins as antigens for EIA method, such as: the need to grow and handle large quantities of live infectious virus; the possibility that the live virus might be incorporated into test materials; the variable nature of the resulting viral lysate; and the substantial number of false positive and false negative results that require additional confirmatory testing. The use of synthetic polypeptides, which can be engineered to immunologically mimic antigenic epitopes of HIV viruses, may avoid some of the above-mentioned disadvantages, but viral antigenic drift could result in the failure to detect HIV infected sera, presumably due to limited presentation of viral epitopes.
Therefore, there remains a need for a reliable, specific and sensitive test for HIV infection that is affordable and practical on a large scale.
There is also an urgent need to develop an effective prophylactic vaccine and other therapeutic strategies to limit HIV transmission as the epidemic continuous unabated. Most successful vaccines consist of either live-attenuated or inactivated viral particles. However, live-attenuation of the HIV-related simian immunodeficiency virus, resulting in protective responses without resulting pathogenicity has not been accomplished, raising safety concerns that make human trial intractable. Also, HIV has many sophisticated mechanisms to evade envelope glycoprotein-directed antibody responses efficiently, including shrouding well-conserved structures by glycan shielding and masking of vulnerable receptor-binding sites by conformational and steric constraints. Therefore, researches turned to envelope glycoprotein-based immunogens as a means of eliciting antibodies, but the use of monomeric gp120 or peptides derived from the immunodominant V3 loop of gp120 can not generate boardly used antibodies but type-specific antibodies.
As a result, the development of an effective detection and prophylactic vaccine against HIV remains an unrealized goal in the effort to contain the current pandemic.